The 27-year-old has been carrying the knock since December, but it was understood that he would return for the Six Nations.

He was handed a call-up to the Wales squad for that particular tournament, but has been forced to undergo an operation that rules out his involvement.

"Following consultation with the medical team Pretorius underwent shoulder reconstruction surgery on Friday, which went well, and the Blues number eight is due to return to full training in May," the statement read.